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Investment Securities - Additional Information (Detail) - USD ($) $ in Thousands | 9 Months Ended |
--- | --- | ---
Sep. 30, 2020 | Sep. 30, 2019 | Dec. 31, 2019
Investments, Debt and Equity Securities [Abstract] |  |  |
Available-for-sale Securities, Gross Realized Gain (Loss), Excluding Other than Temporary Impairments | $ 0 | $ 0 |
Gain Losses Maturities And Impairment | 47 | 15 |
Available-for-sale Securities, Gross Realized Gains | 0 | 0 |
Gross Losses | 0 | 0 |
Gross Gains | 47 | 15 |
Debt Securities, Held-to-maturity, Restricted | 257,600 |  | $ 306,800
Proceeds from Sale of Available-for-sale Securities | 0 | $ 0 |
Debt Securities, Available-for-sale, Restricted | $ 865,100 |  | $ 584,800

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- Definition This item represents the gross gain on maturities of available for sale securities. + References No definition available. + Details
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- Definition This item represents the gross loss on maturities of available for sale securities. + References No definition available. + Details
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- Definition This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. + References No definition available. + Details
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- Definition Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 50 -Paragraph 1A -Subparagraph (b)(1)(i) -URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729 + Details
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